The present invention relates to a cushion spacer to be interposed between glass plates and a stack of glass plates having the cushion spacer. More particularly, the present invention relates to the cushion spacer which can efficiently prevent occurrence of deterioration, scratching, and weathering due to contact between stacked glass plates, aging and friction, and which can be easily inserted between the glass plates and easily removed from the glass plates, and the stack of glass plates with using the cushion spacer.
A cushion spacer for glass plates prevents occurrence of deterioration, scratching, and weathering (discoloring) due to contact between stacked glass plates, long-term storage, and friction by interposing the spacer between the glass plates.
Conventionally known as such a cushion spacer is a spacing sheet paper (Japanese paper made from paper mulberry, so-called SENKASHI paper) (Japanese patent publication JP1-32171B, JP 4-60933B, JP 4-79914B, and JP 2-40798B).
Also known as such a cushion spacer are powders. For example, the following powders have been proposed:
Porous powder (as concrete example, cellulose) (JP 3-53112B);
Cation exchange resin powder (JP 5-78152A);
Globular inorganic powder (from an aluminosilicate and/or other materials) (JP
Chitin and/or chitosan powder (JP 5-339028A);
Zeolite powder (JP 7-2543A); and
Polymethyl methacrylate, polyethylene, polyethylene powder (JP 9-110458A).
Among the conventional cushion spacers as mentioned above, the spacing sheet paper has disadvantages as follows:
i) high cost, because it has to be formed in a predetermined configuration in which area is the same or more than that of the glass plate;
ii) it is difficult to insert the sheet paper between the glass plates, thus making the work complex; and
iii) the glass plate becomes dim and/or spot marks are applied on a glass surface, due to the fats and oils of the sheet paper.
The powder cushion spacers have disadvantages as follows:
I. the glass surface is eroded due to the moisture absorbed in the powder so that burning occurs;
II. there is a possibility of the stacked glass plates slipping from each other and/or the powder coming off a space between the glass plates; and
III. it is difficult to disperse the powder on the glass plate and also remove the powder from the glass plate.
It is an object of the present invention to solve conventional problems mentioned above and to provide a powder cushion spacer which can efficiently prevent occurrence of deterioration, scratching, and weathering (discoloration) due to contact between stacked glass plates, long-term storage and friction, and which can be easily inserted between the glass plates and easily removed from the glass plates and also provide a glass plate stacked body.
A cushion spacer for glass plates of the present invention is made of coconut husk powder, wherein the coconut husk powder is washed by water and then dried, and wherein the spacer is adjusted such that a moisture content of the powder is 10% by weight or less and a fats and oils content of the powder is 1.0% by weight or less, and that the powder interposed between the glass plates brings the friction coefficient between the glass plates of 0.24 or more.
A stack of glass plates of the present invention is formed by interposing the cushion spacer as mentioned above between the glass plates.
The cushion spacer for glass plates of the present invention holds the friction coefficient between the glass plates at 0.24 or more for a long-term period, thereby securely preventing the glass plates from occurrence of deterioration, scratching, and discoloring (weathering) due to contact and friction between stacked glass plates and preventing the glass plates from slipping from each other during transportation. In addition, the cushion spacer is easily inserted between the glass plates and easily removed from the glass plates.
It is important for ensuring the aforementioned friction coefficient that the coconut husk powder is washed by water and then dried to control the moisture content and the fats and oils content. It is preferable that the coconut husk powder comprises particles passing through a 200-mesh sieve in an amount of 95 wt % or more in order to be scattered, dispersed or spread easily and in order to prevent the powder from falling down from the glass plates.
Preferred Embodiments of the Invention
Hereinafter, an embodiment will be described in detail.
The cushion spacer of the present invention provides a friction coefficient of 0.24 or more between the glass plates when it is interposed between glass plates. In case the friction coefficient is below 0.24, slippage may be caused between the glass plates during transportation whereby causing loads shifting. The friction coefficient between the glass plates is preferably 0.25 or more.
The method of measuring the friction coefficient is as described in the section xe2x80x9cExamplesxe2x80x9d described later.
In case the moisture content of coconut husk powder forming the cushion spacer exceeds 10% by weight, the friction coefficient becomes so small as to cause slippage between the glass plates. There is also a possibility of discoloring the glass plate due to the moisture. The moisture content is preferably 8% or less by weight.
In case the fats and oils content of the coconut husk powder exceeds 1.0% by weight, the friction coefficient is reduced with time and it may cause discoloring and/or stain. The fats and oils content is preferably 0.5% by weight or less.
The coconut husk powder according to the present invention is preferably composed of particles in such a manner that 95 wt % or more of the particles pass through a 200-mesh sieve. Coconut husk powder having larger particle sizes in which only less than 95% of the particles pass through the 200-mesh sieve is not scattered, spread or dispersed suitably on the glass surface. In addition, when the glass plates are stacked vertically with such coconut husk powder interposed thercbetween, the coconut husk powder comes off the glass plates thereby losing functions as a spacer.
The coconut husk powder of the present invention has preferably an average particle size between 60 xcexcm and 120 xcexcm. It is more preferable that 50 wt % or more of the coconut husk powder has a particle size between 50 xcexcm and 130 xcexcm.
Further, the coconut husk powder of the present invention is preferably acid weakly to have pH between 6 and 8 in particular 6 and 7 when measured according to JIS-P8133.
The coconut husk powder as mentioned above may be prepared in such a way that coconut husk powder on the market is degreased by washing with water and then dried to adjust the fats and oils and moisture contents thereof and further to adjust particle sizes thereof. It should be noted that the fats and oils contained in the coconut husk powder are water soluble so that they are removed by washing with water.
The degreasing method for adjusting the fats and oils content of the coconut husk powder is not limited to the water washing and drying, but includes a chemical degreasing method by washing or boiling with normal hexane, ethanol, or neutral detergent, and a physical degreasing method by pressing or the like. In terms of the cost, the water washing and drying is most advantageous.
The drying for adjusting the moisture content of the coconut husk powder is made according to the usual process such as natural drying, heated-air drying, and drying in air wind.
It is also quite important to adjust not only the fats and oils content but also the moisture content of the coconut husk powder into a predetermined range. Even with the same samples of the coconut husk powder, in case the moisture contents are different, the fats and oils contents become different so that the friction coefficient becomes less than 0.24.
Degreasing the powder by drying after water washing makes it possible to adjust the fats and oils and moisture contents of the coconut husk powder thereby setting the friction coefficient to 0.24 or more.
Water washing of the coconut husk powder can be conducted by immersing the coconut husk powder and agitating them. In this case, it is preferable that a weight ratio of water/coconut husk power is 20/1 or more. That is, the ratio of the coconut husk power to water is preferably 5% by weight or more. Hereinafter, the weight percentage of the coconut husk powder to water is referred to as xe2x80x9cconcentration for water washingxe2x80x9d. In case the water is less than the above ratio, in other words, the concentration for water washing exceeds 5% by weight, the efficiency of the degreasing is reduced so as not to degrease the coconut husk powder enough. When the concentration for water washing is too low, the efficiency of improving the friction coefficient can not be obtained corresponding to the increase in the amount of water and only the cost is increased. Therefore, the concentration for water washing is preferably 5% by weight or less, particularly between 3 and 5% by weight.
It is preferable to conduct the water washing in such a way that washing time is controlled to obtain a predetermined friction coefficient and that the water washing is repeated at a plurality of times as necessary.
The stack of glass plates according to the present invention comprises a plurality of glass plates and the above coconut husk powder which is dispersed or spread on the glass plates by a conventional dispersing apparatus wherein the glass plates are then stacked. There is no particular limitation on the thickness and the dimension of the glass plates to be stacked.
An amount of the coconut husk powder on the plate is dependent upon the storage term and the storage condition of the stack of glass plates, but normally preferably of 1.0-5.0 g/m2 to the surface area of the glass plates.